Electric discharge device



N v- 3 Y P. LEMAIGRE-VOREAUX .7 ,6

ELECTRIC DISCHARGE DEVICE Filed Oct. 25, 1949 \NVEHTOR P LEM/u em: -\/oREAuX AT TYs.

Patented Nov. 17, 1953 ELECTRIC DISCHARGE DEVICE Pierre Lemaigre-Voreaux, Paris, France, assignor to Societe Anonyme pour les Applications do lElectricite et des Gas Rares-Etablissements Claude-Paz et Silva, Paris, France Application October 25, 1949, Serial No. 123,422

Claims priority, application France November 9, 1948 2 Claims.

My invention deals with an electric discharge tube which may be energized with either alternating or direct current and which is provided at each end with a cap which is of one of two types. A cap of the first type, which I shall name hereafter the neutral type, is such that when plugged into its corresponding socket the contacts of the cap continue to be connected to the same contacts of the socket irrespective of any turning movement of the tube around its longitudinal axis relative to the socket. A cap of the second type, which I shall name hereafter the compulsory type, is such that it can only be inserted into its corresponding socket in one particular way and when so inserted, the tube to which the cap is attached cannot be rotated about its longitudinal axis relative to the socket. I

When direct current is used for energizing a usual type discharge tube provided with two thermo-emissive electrodes, for instance a lowvoltage fluorescent lamp, the rapid formation of a black spot on the envelope of the tube, in the neighbourhood of the positive electrode is noted. This. spot is brought about by the deposition of the thermo-emissive materials of which this electrode is composed. The materials are vaporized from the electrode as a consequence of the high temperature to which the latter is subiected when it functions continuously as an anode.

Discharge tubes have been made with a thermo-emissive cathode at one end and with a cold anode at the other end; these tubes do no exhibit the above-mentioned drawback but they may not be employed on alternating current and in use with direct current care must be paid to polarity when the tubes are connected up, since they may not be turned around end :for end, as the reversing of the electrodes ocoasloned thereby, would prevent them from work- It is an object of the present invention to devise a discharge tube which overcomes the drawbacks mentioned above. According to the present invention there is provided an electric discharge device comprising a gas-filled tube, a cap at each end of the tube, both of said caps be- .ing of one of the types specified and each being .Preferably, each cold electrode is treated to remove gas therefrom prior to its being mounted in the tube. In this way treatment of the electrodes after mounting is avoided. This makes the manufacture of the tube appreciably easier and eliminates the necessity of having to use a high-frequency device for heating the cold electrodes during manufacture.

The cold electrode is located preferably substantially in a plane at right angles to the longitudinal axis of the tube and not further distant from the corresponding cap than the point of the neighbouring thermo-emi'ssive electrode the farthest away from this cap. In this way, the cold electrodes shut out very little radiation and do not change the length of the discharge path.

For a better understanding of the nature of the invention and to show how the same may be carried into effect one constructional form thereof will now be described in greater detail with reference to the accompanying drawings, in which:

Figure 1 is a longitudinal section of an electric discharge tube, provided at each end with a cap of the compulsory type,

Figure 2 is an end viewof the tube, showing the cap utilized in this embodiment,

Figure 3 is a transverse section of the tube, showing the arrangement of the electrodes located at the left end.

Figure 4 is a longitudinal section through one end of an electric discharge tube provided with caps of the "neutral type.

The discharge tube represented on Figures 1, 2, 3 is provided with an envelope I coated on the inside with fluorescent materials and containing argon under a pressure of several millimetres of mercury, together with a small quantity of mercury. At the left-hand of the envelope (as seen in Figure ,1) are placed the thermo-emissive electrode, or cathode 2, connected to the cap contact 8, and the cold electrode, or anode 3, connected to the cap contact 9. Similarly, at the right-hand end are placed the thermo-emissive electrode 4 connected to the contact I 0, and the cold electrode 5 connected to the contact ll. Each thermoemissive electrode 2 or 4, is constituted by a spiral of tungsten wire coated, in the known way, with alkaline earth oxides. Each cold electrode 3 or 5 is a small metal plateinthe form of a slightly curved segment. The plate is placed so that the chord thereof is-near the neighbouring thermoemissive electrode and approximately parallel to the axis'of the latter -(see Figure 3). The average plane 6'or ,1-.(Fig.--1-),-of each cold elec- 3 trod is at right angles to the longitudinal axis of the tube and a little nearer to its corresponding cap 'than the iaxisy'of the neighbour in'g there mo-emis'sive electrode; For a discharge tube in which the normal working current is 0.5 ampere, use may be made, for instance, of coldelectrodes of which each face has asurface area of 1.5 sq. cm.

Each cap of the lamp is-. provided,-in-addition these contacts.

and the corresponding recess determine the-core rect manner in which the cap may be plugged into the corresponding socket. this projection, it is not possible, for example after hay'iii withdrawnth e tub'e"fro'mthe socketsinto which -it was*pi 'operly inserted, to turn the tube al half revo'lution' about its longitudinal axis then toput it back into thesockets-anoperation that would have theresult of connecting the cathodes to the contacts of the; sockets intended forthe' anodes'and viceversa; Oh the other hand, the tube may be withdrawr'i; turned't-hrough' a half-revolution about an axis through the centre of the tube *and" at right angles to the plane of Figure 1,whereafter the caps maybe inserted 'iiitotlie sockets ;"this operation' replaces one cath deep-y theother, an'dho'ne anode by the other.

Use'may be made-or thesame socket's f oreriergizingby direct current and by'ialtern'ating' current but thecon'duct'ors" from the'device f ceding the tube (1. e. the current supply andthe stabilisle'r) must'not be confiectedztqthe am contacts of the soc'ktin'both cases. For the direct current, the socket contact corresponding to the ridnta'ct 8: is connecte for instance, to the negatii e"c tiI'l'dli0136iand the contact corresponding to the contact llto thepositive. conductor. Fo'r er'i'rgiz'ingwith'altrnating current; one" of the conductors is"cbnnect'edto' the socket contact corresponding to the cbntacta',"and theother to the Contact" cbrrsponuihg to" the contact 10.

Figure 4.reprseritsthe'right end ofan electric discharge tube "iovidd with caps of the i'ieutiar type. cap, thelorigitudinal sectionof which is shownon this figure; comprises air-insulatifig pice" lion" tli'efle'fidi ofvvhicli is mounted a brass capsule" M, andbtw'eed this. capsule and the flange of piece i5, is fixed" a brass ring 13 coaxielwithcaps'ule i4and piece i5. .These' metal ieces I3 and {4 are the contacts of thtc'ap. On both ends of the tube; the" Contact pieces or the saine'kirid: capsule or ring, are connected to electrodes of the same type: coldorthermoemi'ssive. Th'isresults in each contact of the sockets, in which arepiaceu thesecaps, remaining connected to an electrode of the "I'riety e when tl'i lamp is turfied'enfdfor'end; moreover, the form oftlfie contacts allows the tube to be turned around its longitudinal 'while leaving the same cap coritactsi'tg'ether h the same; socket contacts.

With alternatin edefine the cold eisetrcdes, (if-which us is not made as main eiectrodea iay be employed as auxiliary electrods intended to facilitate the-starting-of the discharge.

Numerous changes" may be: made, of course,,to the device as described without going outside the scope of the invention. "More particularly, the cap as illustratdmay be replacedby a cap of another-pattern, ofv standard or newtype, pro= aided nowevestnamn the-one handythe turnin On account" of of the tube round its longitudinal axis is not possible, or does not change the electrode connected: to.-.the socket contact: in question, and that," on theothershand,.theiturning round of the tube end for end is possible, but may be executed only for the position that puts each electrode in the position of another electrode of the same type.

The'inven'tio'n applies equally to discharge tubes ofwhich :the envelope is not in the shape of an .elongatedcylinder, for instance when it is made of-sa longttuberandb'ent in the shape of a U or as a spiral; W

What I claim is:

1. An electric discharge device comprising, a rectilinear elongated gas filled tube provided at eachend with an electrode of the thermoemissive kind and with an electrode of the cold kind disposed within the tube close to each other; two caps respectively fixed to the ends of said tube, eachof said caps' being provided with a plurality ofrcontactsurfaces' having the form of surfaces of revolutionhaving a common axis and being located in the prolongation of the tube in the axial direction or saidtube; and at each end-.of the tube a connection between the thermoemissive electrodeofthat end and one 'contact'surface of thecap of that end and a connection between thecold electrodeofthat end and anothercontact surface' of said end, each of said electrodes being connectedto only oneof these contactsurfaces, thosecont'acts of the two caps which are placed in the sameposition relatively to the other parts of the corresponding cap being connectedto anelectrode of the sameki'nd'.

2; An electric discharge device comprising, a rectilinear elongated gas filled tube provided at each end with an electrode of the thermoemi'ssive kind andwith an electrode-of the cold kind disposed withinthetub'e-close to eachother; two caps respectively fixed to the endsof said tube, each of said caps beingprovided with a plurality of contactsurfaces having the form of surfaces of revolution having a common axis-and being located in' the prolongation of the tube' in the axial direction ofsaiditube; at" each end of the tube a connection between the thermoemissive electrode of that end andione" contact surface of the; cap of that end and aconnection between the cold electrode or that end and another contact surface of said end, each of saidelectrodes being connected to only one of, these contact surfaces, those contacts of the" two caps which are placed in the same position relatively to the other parts of the corresponding cap being connected to an electrode of the same kind; and each cold electrode being substantially located in a plane at right angles to the Iongitudinalaxis of the tube, that point of said cold' electrode that is furthest from the provided withthe contact connected with said electrode being not farther from the latter than that point ofvthe thermoemissive electrode connected with another contact. of the same cap which is fiirtlies't away from said cap.

PIERRE: LEMAIGRE-VQREAUX.

References Cited} in the file of'this patent UNITED STATES PATENTS 

